Wim van Egmond
Our featured microscopist for Fall 2003 is accomplished Dutch photomicrographer Wim van Egmond. A multiple winner in the Nikon Small World competition (3rd and 6th in the 2002 contest), van Egmond specializes in microscopy of small water-borne creatures using a variety of advanced contrast-enhancing techniques, such as phase contrast, darkfield, and differential interference contrast. In this arena, Wim's images are some of the best we have seen.
Anemone Larva - Sea anemones are not colonial animals, but it is not unusual to find large numbers of the same species living closely together. This generally occurs because the organisms often reproduce asexually by lateral fission, small clones emerging from the side of a parent anemone and settling nearby. Interestingly, these clones may actively vie for a plot to settle upon in crowded environments and may kill other anemones, including those of their own species.
Brachionus Parasite - Brachionus is a genus of rotifers that reside in a variety of habitats, but are perhaps most often found in hard water lakes. The tiny animals, which only grow about 300 micrometers long, are encased in transparent shells called loricas. Despite their miniscule dimensions, the rotifers in the genus Brachionus have found a notable use in modern society.
Chroococcus Cyanobacteria - Chroococcus is a large genus of cyanobacteria whose species are difficult to differentiate. However, they are typically characterized as living in small colonies of 2, 4, or 8 cells that are surrounded by a clear, mucus sheath. Occasionally unicells or colonies with as many as 16 individuals may occur as well.
Copepod - Approximately 10,000 species of copepods have been identified and the group of organisms exhibits a substantial amount of variation. Though they all lack the compound eyes and carapaces characteristic of most other crustaceans, copepods exist in a multiplicity of forms and may inhabit freshwater and seawater, as well as the moisture between grains of sand or soil and the body tissues of fish and other aquatic organisms.
Copepod Larva - The reproductive process of copepods varies, but is most often sexual. Egg sacks usually develop soon after copulation and are carried outside of the bodies of females. The number of eggs they contain is species dependent, but they generally hatch into larvae after a period of a few days. These early larvae are referred to as nauplii and may be as little as 20 micrometers in diameter.
Coscinodiscus Diatoms - Many diatoms are planktonic, but some species attach to substrates, such as plants or rocks, while others are bottom dwellers. The organisms range in size from approximately 2 micrometers to several millimeters, though only a few exhibit diameters greater than 200 micrometers. Typically, diatoms are divided into two basic categories: the radially symmetric Centrales, such as Coscinodiscus, and elongate, bilaterally symmetric Pennales.
Desmidium swartzii - Desmidium is a genus of filamentous desmids that inhabit freshwater bodies and are common components of the surface material frequently referred to as “pond scum.” The hairlike strands are composed of short cells with deep constrictions and do not feature the spiny projections that may appear among other related genera. A prominent member of the genus is Desmidium swartzii, which is characterized by colonies of triangular cells 11 to 22 micrometers long and 24 to 39 micrometers wide.
Licmophora Diatoms - In addition to their substantial ecological importance, diatoms are noteworthy for their tremendous beauty. Sometimes referred to as the “jewels of the sea,” the microscopic organisms absorb silica from the environment and use it to secrete siliceous shells called frustules. These bivalve, glasslike shells, which are variously shaped and ornamented, have been of interest to microscopists for many years and are sometimes utilized to test the resolving power of microscopes.
Micrasterias - Micrasterias is a genus whose members are considered placoderm desmids, those that feature a cell wall composed of two sections that attach in the mid-region. This type of desmid is also characteristically furnished with pores, spines, granules, or other protuberances. Contrariwise, saccoderm desmids typically possess a smooth, unornamented cell wall that consists of a single piece.
Micrasterias crux-melitensis - The term “desmid” is derived from the Greek “desmos,” meaning “bond” or “chain.” The name originated at a time when the organisms were believed to consist of pairs of joined cells. However, desmids have since been discovered to usually be composed of a single cell that is constricted in the center so that two symmetrical semicells connected by an isthmus are created.
Micrasterias thomasiana - Micrasterias thomasiana is one of the commoner species of its genus and has often been utilized in research. The approximately circular cells are characterized as being large and flat with a deep incision near the median, which divides each organism into two semicells. The semicells are divided into a polar lobe and two lateral lobes that sometimes are divided again.
Odontella Diatoms - Most diatoms are free-living, planktonic species, but some live in extensive colonies or linked into tiny chains, like many members of the genus Odontella. These organisms frequently feature long spines on their frustules and may stay connected to one another after cell division via a crossing of the spines. Other items that may be exhibited on diatom frustules include intricate patterns composed of ridges, round perforations, linear markings, ribs, and vertical canals.
Paramecium - Paramecium is a genus of well-known protozoa whose members typically exhibit slipper-like shapes. Frequent visitors in classrooms and laboratories, an extensive amount of data regarding the microscopic organisms has been collected. As ciliates, paramecia are covered with numerous, short hairlike projections called cilia. The beating of the cilia is what enables the microscopic organisms to locomote through their aquatic environments, as well as to procure their meals.
Polychaete Head - Polychaetes exist in both free-living and tube-dwelling forms, and may vary in size from only a few millimeters long to lengths as great as 10 feet. The segmented worms bear pairs of fleshy appendages called parapodia on most of their segments and the outgrowths are generally equipped with numerous setae, or bristles. Most of the organisms, which often exhibit bright colors, are also outfitted with palps and tentacles on their heads.
Seasparkle (Noctiluca) - Noctiluca species are some of the largest single-celled organisms in the world. The most well known of the genus is Noctiluca scintillans, which may grow from 200 to 2000 microns in diameter. These dinoflagellates possess nearly spherical, balloon-like bodies that lack a pronounced girdle and control their vertical position in the water by regulating their buoyancy, often floating just under the surface of the sea.
Seasparkle (Noctiluca) in Darkfield - Noctiluca scintillans is widely distributed throughout the world, occurring most often in coastal waters. Sometimes referred to as seasparkle, the organisms are often responsible for lighting up the sea, and sometimes the wet sand, at night. The glittering phenomena produced by blooms is believed by some to be a defensive mechanism, acting as a deterrent to predators who want to avoid becoming bioluminescent themselves, an attribute that could make them more readily seen and caught by other organisms.
Snails in Eggs - Snails are well known gastropods that carry their homes on their backs and have a reputation for being slow moving. The organisms, however, have been extremely successful, accomplishing the rare feat of branching out into three different biospheres: freshwater, the oceans, and terra firma. Some tropical species can even be found in the trees, a seemingly unlikely place to look for these lowly creatures.
Stentors - Stentors are sometimes alternatively referred to as trumpet animalcules due to their commonly observed, sessile shape. However, when these organisms are in motion they transform into a less familiar pear or oval-shaped form, locomoting with the help of numerous hairlike cilia. As soon as a suitable substrate or feeding location is encountered, the individuals settle down and resume their prior appearance. In this form, vibrating cilia lining the rim of the trumpet create water currents that draw food particles into the gullet.
Tunicate Larva - The best-known group of tunicates is the ascidians, commonly called sea squirts. These sedentary, globular creatures expel a characteristic jet of water when they are disturbed and can frequently be found attached to a variety of substrates, including rocks, wharves, and boats. Other types of tunicates, however, may be planktonic, swimming or floating freely through the oceans. Colonial forms are also common, and one group, called the larvaceans, retains the characteristics of larvae as adults.
Radiolaria - Typically, radiolaria are more familiar as skeletons than as living creatures. In fact, it was the discovery of ancient tests in the form of a large deposit of ooze along the ocean floor by the nineteenth century Challenger expeditions that first truly revealed their tremendous variation in design, as well as their unique splendor. Some of the hand-drawn illustrations produced from the samples obtained by the ship are so magnificent that they rival many of the photomicrographs of the microscopic creatures taken in modern times.
Volvox Colonies - Worldwide, about 20 species of Volvox have been described. As primary producers, the photosynthetic organisms are an important part of many aquatic ecosystems. For instance, as they convert the energy of the sun into organic molecules and nutrients, they produce dissolved oxygen, a substance needed in significant quantities by many life forms. Moreover, their position at the bottom of the food chain makes them a principle component of the dietary regimens of many aquatic organisms, such as rotifers.
Volvox Connections - Volvox is a genus of colonial organisms that secrete a gelatinous substance called mucilage that binds them together into a hollow sphere. In addition to this extracellular matrix, many Volvox species also exhibit cytoplasmic connections between cells. These cellular bridges are generally considered a sign of greater cellular integration than can be found in most other planktonic colonies, especially since breaking them leads to the death of not only the individuals directly involved, but to the entire group.
Volvox Sperm Packets - The cells in a Volvox colony exhibit a certain amount of differentiation. The individuals towards the front of the colony feature enlarged eyespots, providing them with a greater ability to lead the colony toward sunlight. A small number of specialized cells near the rear of the colony, however, are responsible for reproduction. To facilitate sexual reproduction, some of the gonidia of a Volvox colony may undergo repeated divisions that result in round or oval-shaped sperm packets.
Water Flea - Distributed worldwide, approximately 450 species of water fleas have been identified. The vast majority of the organisms are only found in freshwater, but a small handful can survive in the sea. These marine species may, however, appear quite different than their inland relatives. Typically, water fleas feature a discrete head, a compound eye, pronounced antennae, and a protective carapace that surrounds the trunk and abdomen.
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Photomicrographs are © 2000-2021 by Wim van Egmond.